Contact for ignition systems



July- 21, 1953 S. M. UDALE CONTACT "FOR IGNITION SYSTEMS Filed. 001:. 12, 1951 IN V EN TOR.

Patented July 2!, 1951? 2,6463% CONTACT FOR IGNITIonsYs'rEMs 5 Stanley M. Udale, Detroit, Mich., assignor to Holley Carburetor Company, Detroit, Mich., a

corporation of Michigan Application October 12, 1951, Serial No. 251,077 6 Claims. (01., 200-166) The object of this invention is to'improve the life of contact points in an automotive ignition system of the type which is now in general'use.

Tungsten points are universally used, and recently, a combination of a stationary positive hollow point and a movable'solid point which was negative have been found to give promise of a substantially longer life. To reduce the consumption of tungsten and to still further increase the life of the contact points are the objects of this invention.

siliconized silicon carbide is a refractory material which has less conductivity than tungsten, but is highly refractory. The use of a hollow electrode makes it possible to use a larger area for the other contact so that the lack of conductivity of the carbide may be compensated for by its increased area, specifically, an area three times as great can be provided on the solid side of the contact as compared with the area on the hollow side of the contact. This material is produced by laying a piece of carbon on molten silicon and raising the temperature until a reaction occurs and the carbide of silicon becomes impregnated with silicon. This material has a specific resistance of .003 ohm/cm. cube when the carbon is prepared as follows:

' Per cent Flake graphite 28 Wheat flour 22 Powdered charcoal 10 Casein glue casein) 40 This material is calcined before subjecting it to the silicon treatment. The trade name of this material is Durhy. I

The drawing shows how the invention can be applied to the ordinary ignition. In the figure I0 is the stationary support for a hollow tungsten contact [2. I4 is the movable contact point made of siliconized silicon carbide brazed to a steel arm l6 which carries an insulated rubbing block ll, which is, in its tating cam l8.

The dimensions of the hollow tungsten point I2 are .2" outside diameter, .09 inside and .042" thick. The dimension of the solid siliconized silicon carbide point is .300" outside diameter, and it can have a thickness of about the same as tungsten (.042"), or a little greater. With this combination, the area of the siliconized silicon carbide where it is brazed to the steel arm is three times that of the area of the hollow tungsten point l2, which is brazed to the stationary support l0. siliconized silicon carbide is not, it-

turn, engaged by a roself, a material that can be brazed to steel. It

has first to be impregnated with nickel by the The increase in.

Schoop metal operation process. area of the carbide compensates for the relatively poor electrical conductivity of the siliconized silicon carbide contact withits supporting arm as compared with the conductivity of tungsten and steel.

The stationary contact I2 is preferably made positive, and the siliconized silicon carbide contact I 4 is preferably made negative; although fiat contacts are satisfactory, a spherical surface on the hollow contact is also satisfactory pro viding the curvature in convex. A radius of curvature of two or three inches is. not objectionable for the hollow tungsten point as that ensures line contact on the inner lip of the'hollow Contact.

The stationary support It! is connected to the plate 20 which is mounted on a plate 22 which is moved by rod 24, The arm I6 is mounted on a pin 26 which projects from the plate 20 but is insulated therefrom. Electricity is conducted to' the circuit breaker through a conductor 36. A

condenser 32 is connected across the points by a conductor 34 and a conductor 39, which grounds the stationary contact l2. The rotation of the plate 22 is resisted by the springs 36 and 38 which are connected to stationary pins 40 and, 42. None of these details of the mechanism is part of this invention, which is directed to the Sllbr stitution of siliconized silicon carbide for tungsten and its combination with a hollow tungsten contact point and the provision of an area three' times that of the tungsten, which will reduce the resistance of the carbide.

WhatI claim is: I 1. In an ignition system for internal combustion engines having stationary and a moveable contact, a first metallic and a second non-metallic contact member with substantially flat op-q posed contact surfaces, the first contact member having an opening in the center, through which air may pass and having an area of approximately one-third that of the non-metallic contact which is impe'rforate.

2. A device as set forth in claim ,1 in which the first contact is made of tungstenan-d the second contact is made of siliconized silicon carbide.

3. A device as set forth in claim 1 in which the smaller contact is the stationary one and the movable contact is the largerone.

4. A device as set forth in claim 1 in which the smaller hollow contact is the positive and the negative is the larger contact.

5. In an ignition system for an internal combustion engine, a pair of relatively moveable contact members with substantially fiat opposed contact surfaces having different areas, the contact surface with the smaller area being of tungsten, siliconized silicon carbide being the material for the larger.

6. A pair of contact points comprising an annular tungsten point engaging a larger contact References Cited in the file of this patent UNITED STATES PATENTS Number point made of siliconized silicon carbidewhich 10 latter is imperforate.

STANLEY M.

Name Date Mason l l Jan. 6, 1920 Kent Nov. 1, 1921 Eichenberger Jan. 19, 1932 King Mar. 2, 1937 

